The present work compises the first revision of all Gonadidae distributed worldwide. Under the application of light and scanning microscopy all available types and numerous additional specimens are examined. Extensively illustrated troughout with original line drawings, distribution maps and SEM photographs, the present monograph provides taxonomic keys to the eight valid genera and the 63 valid species, nine of which are described as new. The comprehensive treatment of the anatomy, biology, ecology, history, morphology, philogeny, taxonomy and zoogeography of the Goniadidae makes this a truly enciclopedic work. As such, it is of worldwide relevance to specialists and ecologists alike.